Create fragment processor for performing input color blend with child processor

src/gpu/effects/GrXfermodeFragmentProcessor.cpp

Index: src/gpu/effects/GrXfermodeFragmentProcessor.cpp
diff --git a/src/gpu/effects/GrXfermodeFragmentProcessor.cpp b/src/gpu/effects/GrXfermodeFragmentProcessor.cpp
index ab944d86fcbcb19f1bc157bf753fa135da503e76..942251c980942659b1795a86f85d15734b761dfd 100644
--- a/src/gpu/effects/GrXfermodeFragmentProcessor.cpp
+++ b/src/gpu/effects/GrXfermodeFragmentProcessor.cpp
@@ -9,25 +9,23 @@
 
 #include "GrFragmentProcessor.h"
 #include "effects/GrConstColorProcessor.h"
-#include "gl/GrGLBlend.h"
+#include "gl/GrGLSLBlend.h"
 #include "gl/builders/GrGLProgramBuilder.h"
+#include "SkGr.h"
 
-
-class GrComposeTwoFragmentProcessor : public GrFragmentProcessor {
+class ComposeTwoFragmentProcessor : public GrFragmentProcessor {
 public:
-    GrComposeTwoFragmentProcessor(const GrFragmentProcessor* src, const GrFragmentProcessor* dst,
+    ComposeTwoFragmentProcessor(const GrFragmentProcessor* src, const GrFragmentProcessor* dst,
                     SkXfermode::Mode mode)
         : fMode(mode) {
-        // Only coefficient xfer modes are supported
-        SkASSERT(SkXfermode::kLastCoeffMode >= mode);
-        this->initClassID<GrComposeTwoFragmentProcessor>();
+        this->initClassID<ComposeTwoFragmentProcessor>();
         SkDEBUGCODE(int shaderAChildIndex = )this->registerChildProcessor(src);
         SkDEBUGCODE(int shaderBChildIndex = )this->registerChildProcessor(dst);
         SkASSERT(0 == shaderAChildIndex);
         SkASSERT(1 == shaderBChildIndex);
     }
 
-    const char* name() const override { return "ComposeShader"; }
+    const char* name() const override { return "ComposeTwo"; }
 
     void onGetGLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const override {
         b->add32(fMode);
@@ -37,7 +35,7 @@ public:
 
 protected:
     bool onIsEqual(const GrFragmentProcessor& other) const override {
-        const GrComposeTwoFragmentProcessor& cs = other.cast<GrComposeTwoFragmentProcessor>();
+        const ComposeTwoFragmentProcessor& cs = other.cast<ComposeTwoFragmentProcessor>();
         return fMode == cs.fMode;
     }
 
@@ -57,9 +55,9 @@ private:
 
 /////////////////////////////////////////////////////////////////////
 
-class GrGLComposeTwoFragmentProcessor : public GrGLFragmentProcessor {
+class GLComposeTwoFragmentProcessor : public GrGLFragmentProcessor {
 public:
-    GrGLComposeTwoFragmentProcessor(const GrProcessor& processor) {}
+    GLComposeTwoFragmentProcessor(const GrProcessor& processor) {}
 
     void emitCode(EmitArgs&) override;
 
@@ -69,28 +67,28 @@ private:
 
 /////////////////////////////////////////////////////////////////////
 
-GR_DEFINE_FRAGMENT_PROCESSOR_TEST(GrComposeTwoFragmentProcessor);
+GR_DEFINE_FRAGMENT_PROCESSOR_TEST(ComposeTwoFragmentProcessor);
 
-const GrFragmentProcessor* GrComposeTwoFragmentProcessor::TestCreate(GrProcessorTestData* d) {
+const GrFragmentProcessor* ComposeTwoFragmentProcessor::TestCreate(GrProcessorTestData* d) {
     // Create two random frag procs.
     SkAutoTUnref<const GrFragmentProcessor> fpA(GrProcessorUnitTest::CreateChildFP(d));
     SkAutoTUnref<const GrFragmentProcessor> fpB(GrProcessorUnitTest::CreateChildFP(d));
 
     SkXfermode::Mode mode = static_cast<SkXfermode::Mode>(
-            d->fRandom->nextRangeU(0, SkXfermode::kLastCoeffMode));
-    return SkNEW_ARGS(GrComposeTwoFragmentProcessor, (fpA, fpB, mode));
+        d->fRandom->nextRangeU(0, SkXfermode::kLastMode));
+    return new ComposeTwoFragmentProcessor(fpA, fpB, mode);
 }
 
-GrGLFragmentProcessor* GrComposeTwoFragmentProcessor::onCreateGLInstance() const{
-    return SkNEW_ARGS(GrGLComposeTwoFragmentProcessor, (*this));
+GrGLFragmentProcessor* ComposeTwoFragmentProcessor::onCreateGLInstance() const{
+    return new GLComposeTwoFragmentProcessor(*this);
 }
 
 /////////////////////////////////////////////////////////////////////
 
-void GrGLComposeTwoFragmentProcessor::emitCode(EmitArgs& args) {
+void GLComposeTwoFragmentProcessor::emitCode(EmitArgs& args) {
 
     GrGLFragmentBuilder* fsBuilder = args.fBuilder->getFragmentShaderBuilder();
-    const GrComposeTwoFragmentProcessor& cs = args.fFp.cast<GrComposeTwoFragmentProcessor>();
+    const ComposeTwoFragmentProcessor& cs = args.fFp.cast<ComposeTwoFragmentProcessor>();
 
     // Store alpha of input color and un-premultiply the input color by its alpha. We will
     // re-multiply by this alpha after blending the output colors of the two child procs.
@@ -122,8 +120,8 @@ void GrGLComposeTwoFragmentProcessor::emitCode(EmitArgs& args) {
     SkXfermode::Mode mode = cs.getMode();
     fsBuilder->codeAppend("{");
     fsBuilder->codeAppendf("// Compose Xfer Mode: %s\n", SkXfermode::ModeName(mode));
-    GrGLBlend::AppendPorterDuffBlend(fsBuilder, outputColorSrc.c_str(),
-                                     outputColorDst.c_str(), args.fOutputColor, mode);
+    GrGLSLBlend::AppendMode(fsBuilder, outputColorSrc.c_str(),
+                             outputColorDst.c_str(), args.fOutputColor, mode);
     fsBuilder->codeAppend("}");
 
     // re-multiply the output color by the input color's alpha
@@ -134,21 +132,184 @@ void GrGLComposeTwoFragmentProcessor::emitCode(EmitArgs& args) {
 
 const GrFragmentProcessor* GrXfermodeFragmentProcessor::CreateFromTwoProcessors(
          const GrFragmentProcessor* src, const GrFragmentProcessor* dst, SkXfermode::Mode mode) {
-    if (SkXfermode::kLastCoeffMode < mode) {
-        return nullptr;
-    }
     switch (mode) {
         case SkXfermode::kClear_Mode:
-            return GrConstColorProcessor::Create(GrColor_TRANS_BLACK,
+            return GrConstColorProcessor::Create(GrColor_TRANSPARENT_BLACK,
                                                  GrConstColorProcessor::kIgnore_InputMode);
-            break;
         case SkXfermode::kSrc_Mode:
             return SkRef(src);
-            break;
         case SkXfermode::kDst_Mode:
             return SkRef(dst);
-            break;
         default:
-            return new GrComposeTwoFragmentProcessor(src, dst, mode);
+            return new ComposeTwoFragmentProcessor(src, dst, mode);
+    }
+}
+
+//////////////////////////////////////////////////////////////////////////////
+
+class ComposeOneFragmentProcessor : public GrFragmentProcessor {
+public:
+    enum Child {
+        kDst_Child,
+        kSrc_Child,
+    };
+
+    ComposeOneFragmentProcessor(const GrFragmentProcessor* dst, SkXfermode::Mode mode, Child child)
+        : fMode(mode)
+        , fChild(child) {
+        this->initClassID<ComposeOneFragmentProcessor>();
+        SkDEBUGCODE(int dstIndex = )this->registerChildProcessor(dst);
+        SkASSERT(0 == dstIndex);
+    }
+
+    const char* name() const override { return "ComposeOne"; }
+
+    void onGetGLProcessorKey(const GrGLSLCaps& caps, GrProcessorKeyBuilder* b) const override {
+        GR_STATIC_ASSERT((SkXfermode::kLastMode & SK_MaxU16) == SkXfermode::kLastMode);
+        b->add32(fMode | (fChild << 16));
+    }
+
+    SkXfermode::Mode mode() const { return fMode; }
+
+    Child child() const { return fChild; }
+
+protected:
+    bool onIsEqual(const GrFragmentProcessor& that) const override {
+        return fMode == that.cast<ComposeOneFragmentProcessor>().fMode;
+    }
+
+    void onComputeInvariantOutput(GrInvariantOutput* inout) const override {
+        SkXfermode::Coeff skSrcCoeff, skDstCoeff;
+        if (SkXfermode::ModeAsCoeff(fMode, &skSrcCoeff, &skDstCoeff)) {
+            GrBlendCoeff srcCoeff = SkXfermodeCoeffToGrBlendCoeff(skSrcCoeff);
+            GrBlendCoeff dstCoeff = SkXfermodeCoeffToGrBlendCoeff(skDstCoeff);
+            GrInvariantOutput childOutput(0xFFFFFFFF, kRGBA_GrColorComponentFlags, false);
+            this->childProcessor(0).computeInvariantOutput(&childOutput);
+            GrColor blendColor;
+            GrColorComponentFlags blendFlags;
+            if (kDst_Child == fChild) {
+                GrGetCoeffBlendKnownComponents(srcCoeff, dstCoeff,
+                                               inout->color(), inout->validFlags(),
+                                               childOutput.color(), childOutput.validFlags(),
+                                               &blendColor, &blendFlags);
+            } else {
+                GrGetCoeffBlendKnownComponents(srcCoeff, dstCoeff,
+                                               childOutput.color(), childOutput.validFlags(),
+                                               inout->color(), inout->validFlags(),
+                                               &blendColor, &blendFlags);
+            }
+            // will the shader code reference the input color?
+            GrInvariantOutput::ReadInput readsInput = GrInvariantOutput::kWillNot_ReadInput;
+            if (kDst_Child == fChild) {
+                if (kZero_GrBlendCoeff != srcCoeff || GrBlendCoeffRefsSrc(dstCoeff)) {
+                    readsInput = GrInvariantOutput::kWill_ReadInput;
+                }
+            } else {
+                if (kZero_GrBlendCoeff != dstCoeff || GrBlendCoeffRefsDst(srcCoeff)) {
+                    readsInput = GrInvariantOutput::kWill_ReadInput;
+                }
+            }
+            inout->setToOther(blendFlags, blendColor, readsInput);
+        } else {
+            inout->setToUnknown(GrInvariantOutput::kWill_ReadInput);
+        }
+    }
+
+private:
+    GrGLFragmentProcessor* onCreateGLInstance() const override;
+
+    SkXfermode::Mode    fMode;
+    Child               fChild;
+
+    GR_DECLARE_FRAGMENT_PROCESSOR_TEST;
+
+    typedef GrFragmentProcessor INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+class GLComposeOneFragmentProcessor : public GrGLFragmentProcessor {
+public:
+    GLComposeOneFragmentProcessor(const GrProcessor& processor) {}
+
+    void emitCode(EmitArgs& args) override {
+        GrGLFragmentBuilder* fsBuilder = args.fBuilder->getFragmentShaderBuilder();
+        SkXfermode::Mode mode = args.fFp.cast<ComposeOneFragmentProcessor>().mode();
+        ComposeOneFragmentProcessor::Child child =
+            args.fFp.cast<ComposeOneFragmentProcessor>().child();
+        // declare _dstColor and emit the code for the two child
+        fsBuilder->codeAppendf("vec4 _child;");
+        this->emitChild(0, nullptr, "_child", args);
+
+        const char* inputColor = args.fInputColor;
+        // We don't try to optimize for this case at all
+        if (!inputColor) {
+            fsBuilder->codeAppendf("const vec4 ones = vec4(1);");
+            inputColor = "ones";
+        }
+
+        // emit blend code
+        fsBuilder->codeAppend("{");
+        fsBuilder->codeAppendf("// Compose Xfer Mode: %s\n", SkXfermode::ModeName(mode));
+        if (ComposeOneFragmentProcessor::kDst_Child == child) {
+            GrGLSLBlend::AppendMode(fsBuilder, inputColor, "_child", args.fOutputColor, mode);
+        } else {
+            GrGLSLBlend::AppendMode(fsBuilder, "_child", inputColor, args.fOutputColor, mode);
+        }
+        fsBuilder->codeAppend("}");
+    }
+
+private:
+    typedef GrGLFragmentProcessor INHERITED;
+};
+
+/////////////////////////////////////////////////////////////////////
+
+GR_DEFINE_FRAGMENT_PROCESSOR_TEST(ComposeOneFragmentProcessor);
+
+const GrFragmentProcessor* ComposeOneFragmentProcessor::TestCreate(GrProcessorTestData* d) {
+    // Create one random frag procs.
+    // For now, we'll prevent either children from being a shader with children to prevent the
+    // possibility of an arbitrarily large tree of procs.
+    SkAutoTUnref<const GrFragmentProcessor> dst(GrProcessorUnitTest::CreateChildFP(d));
+    SkXfermode::Mode mode = static_cast<SkXfermode::Mode>(
+        d->fRandom->nextRangeU(0, SkXfermode::kLastMode));
+    ComposeOneFragmentProcessor::Child child = d->fRandom->nextBool() ?
+        ComposeOneFragmentProcessor::kDst_Child :
+        ComposeOneFragmentProcessor::kSrc_Child;
+    return new ComposeOneFragmentProcessor(dst, mode, child);
+}
+
+GrGLFragmentProcessor* ComposeOneFragmentProcessor::onCreateGLInstance() const {
+    return new GLComposeOneFragmentProcessor(*this);
+}
+
+//////////////////////////////////////////////////////////////////////////////
+
+const GrFragmentProcessor* GrXfermodeFragmentProcessor::CreateFromDstProcessor(
+    const GrFragmentProcessor* dst, SkXfermode::Mode mode) {
+    switch (mode) {
+        case SkXfermode::kClear_Mode:
+            return GrConstColorProcessor::Create(GrColor_TRANSPARENT_BLACK,
+                                                 GrConstColorProcessor::kIgnore_InputMode);
+        case SkXfermode::kSrc_Mode:
+            return nullptr;
+        default:
+            return new ComposeOneFragmentProcessor(dst, mode,
+                                                   ComposeOneFragmentProcessor::kDst_Child);
+    }
+}
+
+const GrFragmentProcessor* GrXfermodeFragmentProcessor::CreateFromSrcProcessor(
+    const GrFragmentProcessor* src, SkXfermode::Mode mode) {
+    switch (mode) {
+        case SkXfermode::kClear_Mode:
+            return GrConstColorProcessor::Create(GrColor_TRANSPARENT_BLACK,
+                                                 GrConstColorProcessor::kIgnore_InputMode);
+        case SkXfermode::kDst_Mode:
+            return nullptr;
+        default:
+            return new ComposeOneFragmentProcessor(src, mode,
+                                                   ComposeOneFragmentProcessor::kSrc_Child);
     }
 }